1. Field of the Invention
The present invention relates to a power source device.
2. Description of the Related Art
In the related art, a technology of storing a generated electric charge and providing the stored electric charge to a load as a current to operate the load is known (for example, refer to Japanese Unexamined Patent Application No. 2007-181278).
FIG. 5 is a diagram showing an example of a functional configuration of a power source device 100 of the related art. The power source device 100 includes a power generation element 10, a capacitor 20, a diode 110, a voltage detection circuit 30, a timer circuit TM, a logical multiplication circuit AND, a switch SW, and a voltage control circuit VR.
The power source device 100 supplies power generated by the power generation element 10 to a terminal T8 of a load LD. The power which is generated by the power generation element 10 and is output from a terminal T1 is supplied to the capacitor 20 as a current I1 flowing through a wire L1 and a current I2 flowing through a wire L2. The capacitor 20 accumulates electric charges generated by the power generation element 10. The storage power stored in the capacitor 20 is supplied to the voltage control circuit VR as a current I11. The capacitor 20 is grounded via a wire L3. The diode 110 prevents a backflow of a current from the capacitor 20 when the power generation element 10 does not generate electricity. The timer circuit TM controls time of an intermittent operation of supplying power to the load LD. The logical multiplication circuit AND outputs a logical multiplication of an output from a terminal T3 of the voltage detection circuit 30 and an output from the timer circuit TM. The switch SW is turned on and off by the output of the logical multiplication circuit AND. The voltage control circuit VR controls a voltage supplied to the load LD.
In the example shown in FIG. 5, the voltage detection circuit 30 detects a charged voltage of the capacitor 20 at a terminal T2 (voltage detection terminal). The switch SW is turned on when the charged voltage is equal to or higher than voltage which can operate the load LD and an output from the timer circuit TM is generated. The switch SW is turned on, and thus, the storage power of the capacitor 20 is supplied to the load LD via the voltage control circuit VR as a current I7.
Meanwhile, in the example shown in FIG. 5, the operation of the load LD on the storage power of the capacitor 20 decreases the charged voltage of the capacitor 20. When the charged voltage of the capacitor 20 becomes lower than the minimum operation voltage of the load LD, the load LD cannot operate. The load LD can thus operate as long as the charged voltage of the capacitor 20 is equal to or higher than the minimum operation voltage of the load LD.
In the example shown in FIG. 5, when the charged voltage of the capacitor 20 becomes lower than the minimum operation voltage of the load LD, the power stored in the capacitor 20 cannot be used anymore for the operation of the load LD. Accordingly, in the above-described case, the power stored in the capacitor 20 is wasted.
Considering the amount of the storage power which cannot be used for the operation of the load LD, the size of the entire power source device 100 consequently increases since it is necessary to adopt a larger capacitor for the capacitor 20 in the example shown in FIG. 5. In a case where the size of the capacitor 20 increases, a period during which the capacitor 20 is charged until the load LD can operate becomes longer after the capacitor 20 is discharged.
In the above-described related art, when the voltage of the storage power becomes lower than the voltage required for the operation of the load, the storage power cannot be used, and thus, becoming a waste.
An object of the present invention is to provide a power source device which can use more storage power.